Apparatus for steam degreasing

ABSTRACT

Oily articles are degreased by being immersed into the vapour of a boiling solvent, such as trichloroethylene. Immediately after the articles have entered into said vapour they are exposed to a powerful jet of oily solvent. Said oily solvent jet removes foreign particles adhering to the surface of the articles.

H0110 et a1. [45] Apr, 1, 1972 [54] APPARATUS FOR STEAM [5 6] ReferencesCited DEGREASING UNITED STATES PATENTS [72] Inventors: Kurt Anders Helm;Rune Einar l-lansson, 3,460,990 8/1969 Barday ..134/11 X both ofSkoghall; Bengt Gunner Berglund, 1,907,875 5/1933 Robertson... ..134/11X Hammaro, all of Sweden 3,350,734 11/1967 Holm ....134/122 X 3,491,7781 1970 L h rt t l. ..134 64 73 Assignee: 0111101011115 Aktiebolag,Uddeholms, e e a Sweden Primary Examiner-Robert L. Bleutge [22] Filed:Mar. 20 1970 Attorney-Pierce, Scheffler & Parker [21] Appl. No.: 21,237[57] ABSTRACT Oily articles are degreased by being immersed into thevapour 52 0.5.131 ..134/64,134/108,134/109 of a-boiling solvemisuch astrichloroethylene- Immediately [5 1] 02 0g o0 after the articles haveentered into said vapour they are ex- [58] Field of Search ..134/11, 15,64, 122, 108, 109 to a PQWerful J of Oily S Said Oily Solvent J removesforeign particles adhering to the surface of the articles.

3 Claims, 1 Drawing Figure P'A'TE'I JTEnAPn 18 I972 INVENTORS KurfAnder:Helm Rune Emar Hansson Ben i Gunnar Bergland B M Afi APPARATUS FOR STEAMDEGREASWG The invention relates to an apparatus for degreasing articles,preferably metal articles, by immersing them in vapor from a boilingsolvent, preferably trichloroethylene or tetrachloroethylene. The vaporcondenses on the relatively cool articles and oil and other fat istherefore dissolved in the condensed solvent and runs off the articles.

It has been found with degreasing of this type that small solidparticles have a strong tendency to adhere firmly to the articlesalthough the oil is removed satisfactorily. When sheet metal is beingdegreased, for example, such particles may have remained from when thesheet metal was rolled. Particles of foreign origin may also haveadhered to the article, for example due to dust.

Attempts have been made to remove such particles from the articles byfinishing off the degreasing process by rinsing the articles in cleansolvent. Not even if the solvent was sprayed on to the articles underhigh pressure have all particles been successfully removed. Remainingparticles are a disadvantage for instance if the articles are to bepainted or subjected to electrolytic treatment.

It has now been found, according to the present invention, that adherentparticles can be effectively removed from articles if they are rinsedwith liquid solvent, preferably containing oil, immediately after theyhave been immersed in the solvent vapor. The explanation of thefavourable technical result achieved is probably that the solidparticles can easily move about on the surface of the articles as longas the oil film present acts as a lubricant, so to speak. If, however,the oil film is first removed by condensation of the solvent vapor theparticles come into direct contact with the surface of the articles andthus such electrostatic forces come into operation that the particlesare bound rather firmly to the surface.

The apparatus according to the invention is thus characterized in that avessel is arranged to collect oily solvent running off the articles andthat a pump is arranged to pump the oily solvent from the vessel tonozzles which are situated at the top in the vapor space and which aredirected towards the place where the articles are lowered into the vaporspace, whereupon the articles are exposed to a strong jet of oil solventimmediately after they have been immersed in the vapor and before allthe oil has'had time to be dissolved from the surface of the articles.

The invention can be used for manually operated degreasing apparatuses,in use sporadically, the operator in this case spraying solvent on thearticles by means of a manually operated rinsing nozzle immediatelyafter they have been surrounded by the vapor. In order to avoid the airabove the vapor being filled with vapor the operator should hold therinsing nozzle below the level of the vapor. The rinsing nozzle maysuitably be arranged to be connected as desired either to the oilysolvent in the apparatus or to clean solvent, preferably that which isformed when the vapor condenses on the cooling means normally used todetermine the highest level of the vapor.

The invention can also be applied in an apparatus in which the articlesare automatically carried by a transport means into and out of the vaporzone.

An example of such an apparatus is shown in the accompanying drawing.

The apparatus illustrated is intended for continuous degreasing of asteel strip, but may be modified so that the steel strip is replaced byan endless conveyor which carries the articles to be degreased.

A container 1 has a zone 2 at the bottom for liquid solvent, in which isa heating element 4 for boiling the solvent. The vapor from the solventrises into a vapor zone 3, the highest level of which is determined by awall 10, the upper edge of this forming an overflow. When the heavysolvent vapor runs over this overflow, or comes into contact with thecooling pipe 11 on which it condenses, the condensate runs to a vessel13 through a tube 12.

The strip to be degreased is led down into the container 1 over rollers7, deflected around a roller 6 in the vapor zone,

and led out of the container over rollers 8. At the points where thestrip is led into and out of the degreasing apparatus, suction boxes 9are arranged to prevent solvent vapor from leaking out into thesurroundings.

Immediately after the strip has entered into the vapor zone 3 it passesbetween two pipes 25 which are perforated on the side facing the strip.The pipes 25 are situated 300 mm. below the upper edge of the wall 10.The pipes 25 are in communication with a pump 22 via a filter 23 and thesuction side of the pump is connected to a tank 21 for oily solvent. Thevessel 21 is separated from the boiling zone 2 by a wall 24. The vaporzone 3 has a substantially horizontal tray-like wall 26 which collectsliquid solvent and oil solvent and directs it to the vessel 21.

At the point where the strip 5 leaves the vapor zone 3 wipers 14 arearranged which operate across the entire width of the strip on the upperand lower sides. The wipers may consist of brushes or, for examplehorse-hair or nylon, or of a resilient lip of, for example, leather orplastic. The wipers are placed so that they touch the strip 5 at thelevel defined by the upper edge of the wall 10.

In the vapor zone 3, between the roller 6 and the wipers 14, two pipes15 are arranged extending horizontally across the entire width of thestrip on its upper and lower sides. 0n the side facing the strip thepipes 15 are provided with perfora tions or spray nozzles. Via conduct16 the pipes 15 are in communication with a pump 17 which is fed withcondensate from the previously mentioned vessel 13. The conduit 16communicates with the vessel 13 via a valve 19 which is regulated by afloat 20 situated in the vessel 13. When the level of the solvent in thevessel 13 is low, the valve 19 is opened, and when the level is high itis closed.

The apparatus described operates in the following manner. The strip 5 isfed through the degreasing apparatus in the direction of the arrow. Whenthe relatively cool strip comes into the vapor zone 3 the vapor from thesolvent starts to condense on the strip. The condensate dissolves oiland other fat on the strip and runs back to the liquid zone 2. Beforeall the oil has had time to be dissolved, however, the strip has hadtime to be exposed to a powerful jet of oily solvent from the perforatedpipes 25. Adherent solid particles are thus effectively removed. Thestrip 5, which is still relatively cool, continues into the vapor zone 3where the remainder of the oil is removed by the condensing solventvapor. The cleaning result is further improved by the condensate whichmay be sprayed onto the strip through the pipes 15. Solvent which mayremain on the strip when it leaves the vapor zone is removed by thewiper 14. In this way there is little mixing of air and solvent vaporand the quantity of solvent vapor which is wasted through the suctionboxes 9 can be kept low. When a thick strip is being degreased a greatquantity of solvent will condense on the strip and the amount of solventwhich condenses on the cooling tubes 11 and flows to the vessel 13 willthen be relatively small, so that the level in the tank 13 drops. Thefloat 20 then opens the valve 19 so that some, possibly all the solventfrom the pump 17 is pumped back into the vessel 13 via the tube 18. Itis thus guaranteed that the pump 17 is always fed with solvent.

We claim:

1. Apparatus for degreasing strip material comprising a container, awall in the bottom of said container for dividing the lower portionthereof into a first and a second open compartment for collectingdegreasing solvent, means for heating the solvent in said firstcompartment for vaporizing at least a portion of the solvent therein toform a vapor zone in the upper portion of said container, condensermeans at the top of said container for condensing vapors at the top ofthe vapor zone to delimit the upper surface of the vapor zone, means forreturning the condensed vapor to said second compartment, means fortransporting strip material to be degreased in a V- shaped pathdownwardly into the vapor zone on one side of said container and thenupwardly out of the vapor zone on the opposite side of the container,spray means disposed in the and overflow said dividing wall into saidfirst compartment for collection of contaminants and for revaporizationof solvent therefrom.

2. Apparatus as claimed in claim 1 wherein said spray means are disposedfrom about mm. to 300 mm. below the upper surface of the vapor zone.

3. Apparatus as claimed in claim 1 and further comprising a filter meansfor removing solid contaminants from the oily solvent being pumped tosaid spray means.

a v s v

2. Apparatus as claimed in claim 1 wherein said spray means are disposedfrom about 100 mm. to 300 mm. below the upper surface of the vapor zone.3. Apparatus as claimed in claim 1 and further comprising a filter meansfor removing solid contaminants from the oily solvent being pumped tosaid spray means.